Etchant for etching double-layered copper structure and method of forming array substrate having double-layered copper structures

ABSTRACT

An etchant for forming double-layered signal lines and electrodes of a liquid crystal display device includes hydrogen peroxide (H 2 O 2 ), a phosphate, F-ions, an organic acid having a carboxyl group (—COOH), a copper (Cu) inhibitor, and a hydrogen peroxide (H 2 O 2 ) stabilizer, wherein each of the double-layered signal lines and electrodes of the liquid crystal display device includes a first layer of one of aluminum (Al), aluminum alloy (Al-alloy), titanium (Ti), titanium alloy (Ti-alloy), tantalum (Ta), and a tantalum alloy (Ta-alloy) and a second layer of copper (Cu).

[0001] The present invention claims the benefit of Korean PatentApplication No. 2003-0041162, filed in Korea on Jun. 24, 2003, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an array substrate forelectronic equipment, and more particularly, to an etchant and anetching method for liquid crystal display (LCD) devices.

[0004] 2. Discussion of the Related Art

[0005] In general, metal lines in electronic equipment generally serveto apply signals to electronic elements. However, the metal linescontribute to production costs and stability of the electronicequipment. Accordingly, a material to form the metal lines needs to beinexpensive, have a low electrical resistance, and a high corrosionresistance.

[0006] Array substrates are commonly used in LCD devices, whereinperformance characteristics and operational properties of the arraysubstrates are partially determined by the material with-whichindividual elements of the array substrates are formed. For example,gate and data lines of the array substrate significantly influence theperformance characteristics and operational properties of the arraysubstrate. Although the resistance of the materials used to form thegate and data lines is relatively insignificant in small-sized LCDdevices, the resistance of the gate and data lines in large-sized LCDdevices is directly dependent upon image quality. Thus, in large-sizedLCD devices having high resolution, materials with which to form thegate and data lines includes aluminum (Al) or Al-alloys due to their lowelectrical resistance.

[0007] However, pure aluminum is chemically weak when exposed to acidicprocessing, and may result in formation of hillocks on surfaces of thegate line and gate electrode during high temperature processing.Furthermore, the occurrence of hillocks may cause extraordinary growthof a gate insulation layer subsequently formed on the gate line and gateelectrode. Thus, the gate insulation layer may be destroyed, and anelectrical short circuit may be created between the gate electrode andan active layer that is subsequently formed on the gate insulationlayer. Accordingly, thin film transistors (TFTs) having gate lines andgate electrodes formed from pure aluminum do not adequately function asswitching devices.

[0008]FIG. 1 is a perspective view of a transflective LCD deviceaccording to the related art. In FIG. 1, a transflective LCD device 11includes upper and lower substrates G1 and G2 with an interposed liquidcrystal layer 70. For example, the upper and lower substrates G1 and G2are commonly referred to as color filter and array substrates,respectively.

[0009] On a surface of a substrate 5 facing the array substrate G2, thecolor filter substrate G1 sequentially includes a black matrix 6 and acolor filter layer 7. The color filter layer 7 includes a matrix arrayof red (R), green (G), and blue (B) color filters, and the black matrix6 is disposed among the matrix array of red (R), green (G), and blue (B)color filters, such that each color filter is divided by the blackmatrix. In addition, a common electrode 18 is disposed on both the colorfilter layer 7 and the black matrix 6.

[0010] On a surface of a substrate 21 facing the upper substrate G1, thearray substrate G2 includes an array of TFTs T (in FIG. 2) that functionas switching devices. The array of TFTs is formed to correspond to thematrix array of red (R), green (G) and blue (B) color filters, wherein aplurality of gate and data lines 33 and 53 are positioned to cross eachother and the TFT T is located near the crossing portion of the gate anddata lines 33 and 53. In addition, the lower substrate G2 includes aplurality of pixel regions P that are defined by the crossing of thegate and data lines 33 and 53, wherein a pixel electrode 69 is disposedwithin the pixel regions P.

[0011]FIG. 2 is an enlarged plan view of a portion “S” of FIG. 1according to the related art. In FIG. 2, the TFT T includes a gateelectrode 31, an active layer 39, a source electrode 49, and a drainelectrode 51. The gate electrode 31 is elongated from the gate line 33,and the source electrode 49 is elongated from the data line 53. Inaddition, the active layer is disposed over the gate electrode 31between the source and drain electrodes 49 and 51, and the drainelectrode 51 is spaced apart from the source electrode 49 across thegate electrode 31.

[0012] In FIGS. 1 and 2, the common electrode 18 and the pixel electrode69 are all formed of a transparent conductive material having good lighttransmissivity, such as indium tin oxide (ITO). The LCD device of FIGS.1 and 2 utilizes optical anisotropy and polarization characteristics ofliquid crystal molecules of the liquid crystal layer 70 to createimages, wherein the liquid crystal molecules have specific alignmentdirections due to their inherent physical properties. Accordingly, sinceincident light may be refracted by the alignment of the liquid crystalmolecules to form the images and the specific alignment directions ofthe liquid crystal molecules may be modified by application of anelectric field, creation of the images may be easily controlled bychanging the electric field. In addition, the material for forming thegate and data lines 33 and 53 is significantly important. For example,if the gate and data lines 33 and 53 are formed of a metallic materialhaving a high electrical resistance, signal delays may be generatedalong the gate and data lines 33 and 53, thereby misaligning the liquidcrystal molecules and preventing the images from properly being created.Thus, image resolution of the LCD device may be reduced.

[0013]FIG. 3 is a cross sectional view along III-III of FIG. 1 accordingto the related art. In FIG. 3, a switching region T and a pixel region Pare defined on a substrate 21 by the gate electrode 31 and the gate line33 formed on the substrate 21. For example, the gate line 33 is disposedalong a first direction adjacent to the pixel region P, and the gateelectrode 31 extends from the gate line 33 into the switching region T.Then, a gate insulating layer 36 is formed on the substrate 21 to coverthe gate electrode 31 and the gate line 33, and an active layer 39 ofamorphous silicon and an ohmic contact layer 41 of doped amorphoussilicon are sequentially formed on the gate insulating layer 36,especially over the gate electrode 31. Next, the source and drainelectrodes 49 and 51 are disposed on the ohmic contact layer 41 andspaced apart from each other across the gate electrode 31. Accordingly,the data line 53 is connected to the source electrode 49 and extends onthe gate insulating layer 36, and the data line 53 crosses the gate line33 and defines the pixel region P (in FIG. 1). Next, a portion of theohmic contact layer 41 between the source and drain electrodes 49 and 51is eliminated to expose the underlying active layer 39. A passivationlayer 59 is formed on the gate insulating layer 36 to cover the sourceelectrode 49, the drain electrode 51, and the data line 53. In addition,the passivation layer 59 has a drain contact hole 61 that exposes aportion of the drain electrode 51. Then, the pixel electrode 69 of atransparent conductive material is formed on the passivation layer 59within the pixel region P, and contacts the drain electrode 51 throughthe drain contact hole 61.

[0014] In FIG. 3, the gate electrode 31 and the gate line 33 are formedof aluminum (Al) or an aluminum alloy, such as AlNd. However, aspreviously described, aluminum is chemically weak and causes formationof hillocks. In order to overcome those disadvantages of using aluminum,chromium (Cr) or molybdenum (Mo), each of which has a strong chemicalproperties in acidic processes, is frequently used for the gate and datalines. However, forming the gate electrode 31 and the gate line 33 of Cror Mo causes signal delays due to their high electrical resistance.Furthermore, if a double-layered structure of Al and Cr/Mo is used toform the gate and data lines 33 and 53, an etchant for simultaneouslyetching the double-layered structure is required and a process foretching the double-layered structure must be adjusted. In addition, if adouble-layered structure of Al and Cr/Mo is used to form the gate anddata lines 33 and 53, and if the Al layer and the Cr/Mo layer areseparately etched, two separate process steps are necessary to etch thedouble-layered structure of Al and Cr/Mo, thereby complicatingfabrication processes and decreasing manufacturing yield.

SUMMARY OF THE INVENTION

[0015] Accordingly, the present invention is directed to an etchant foretching a double-layered copper structure and a method of forming anarray substrate having double-layered copper structures thatsubstantially obviates one or more of the problems due to limitationsand disadvantages of the related art.

[0016] An object of the present invention is to provide an etchant thatsimultaneously etches double-layered metal layer structures.

[0017] Another object of the present invention is to provide a method offorming an array substrate having copper lines and electrodes.

[0018] Additional features and advantages of the invention will be setforth in the description which follows and in part will be apparent fromthe description, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0019] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, anetchant for forming double-layered signal lines and electrodes of aliquid crystal display device includes hydrogen peroxide (H₂O₂), aphosphate, F-ions, an organic acid having a carboxyl group (—COOH), acopper (Cu) inhibitor, and a hydrogen peroxide (H₂O₂) stabilizer,wherein each of the double-layered signal lines and electrodes of theliquid crystal display device includes a first layer of one of aluminum(Al), aluminum alloy (Al-alloy), titanium (Ti), titanium alloy(Ti-alloy), tantalum (Ta), and a tantalum alloy (Ta-alloy) and a secondlayer of copper (Cu).

[0020] In another aspect, a method of forming an array substrate of aliquid crystal display device includes forming a first metallic layer ona substrate, forming a first copper (Cu) layer on the first metalliclayer, patterning the first metallic layer and the first Cu layersimultaneously using a first etchant to form a gate line and a gateelectrode, the first etchant includes hydrogen peroxide (H₂O₂), aphosphate, F-ions, an organic acid having a carboxyl group (—COOH), acopper (Cu) inhibitor, and a hydrogen peroxide (H₂O₂) stabilizer,forming a gate insulating layer over an entire surface of the substrateto cover the gate line and the gate electrode, forming an active layerand an ohmic contact layer on the gate insulating layer and over thegate electrode, forming a second metallic layer and a second copper (Cu)layer over the gate insulating layer to cover the active layer and theohmic contact layer, patterning the second metallic layer and the secondCu layer simultaneously using a second etchant to form a sourceelectrode, a drain electrode, and a data line, the second etchantincludes hydrogen peroxide (H₂O₂), a phosphate, F-ions, an organic acidhaving a carboxyl group (—COOH), a copper (Cu) inhibitor, and a hydrogenperoxide (H₂O₂) stabilizer, forming a passivation layer over the gateinsulating layer to cover the source and drain electrodes and the dataline, the passivation layer having a drain contact hole exposing aportion of the data line, and forming a pixel electrode on thepassivation layer, the pixel electrode contacting the drain electrodethrough the drain contact hole.

[0021] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate the presentinvention and together with the description serve to explain theprinciples of that invention. In the drawings:

[0023]FIG. 1 is a perspective view of a transflective LCD deviceaccording to the related art;

[0024]FIG. 2 is an enlarged plan view of a portion “S” of FIG. 1according to the related art;

[0025]FIG. 3 is a cross sectional view along III-III of FIG. 1 accordingto the related art;

[0026]FIG. 4 is a graph showing an exemplary relationship between etchtimes of a copper layer and concentrations of hydrogen peroxide (H₂O₂)according to the present invention;

[0027]FIG. 5 is a graph showing another exemplary relationship betweenetch times of a copper layer and concentrations of potassium dihydrogenphosphate (KH₂PO₄) according to the present invention;

[0028]FIG. 6 is a graph showing another exemplary relationship betweenetch times of a copper layer and concentrations of 4-methylimidazole(C₄H₆N₂) according to the present invention;

[0029]FIG. 7 is a graph showing another exemplary relationship betweenetch times of metallic layers and concentrations of ammonium bifluoride(NH₄HF₂) according to the present invention;

[0030]FIG. 8 is a photomicrograph showing an exemplary interfacialcondition between a partially-etched copper/aluminum alloy (Cu/Al-alloy)double layer and an overlaying insulator according to the presentinvention;

[0031]FIG. 9 is a photomicrograph showing an exemplary slope of apartially-etched copper/aluminum alloy (Cu/Al-alloy) double layeraccording to the present invention;

[0032]FIG. 10 is a photomicrograph of an exemplary partially-etchedcopper/aluminum alloy (Cu/Al-alloy) double layers according to thepresent invention; and

[0033]FIGS. 11A to 11EC are cross sectional views of an exemplary methodof fabricating of an array substrate according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0035] According to the present invention, an etchant may be providedfor etching copper-aluminum (Cu—Al), copper-titanium (Cu—Ti), orcopper-tantalum (Cu—Ta) double layer structures, or multiple layersthereof. The etchant may include hydrogen peroxide (H₂O₂), phosphoricacid (or phosphate), and F-ion (e.g., ammonium bifluoride (NH₄HF₂)),0.01-5%). Furthermore, the etchant may include hydrogen peroxides(H₂O₂), phosphoric acids (or phosphate), organic acid having carboxylgroups (—COOH), copper (Cu) inhibitors, H₂O₂ stabilizers, and additives.The additives included in the etchant may function to improve etchingcharacteristics, such as etching time and etching efficiency.

[0036] The phosphates included in the etchant may be represented by achemical formula of A_(X)H_(Y)PO₄, wherein “A” may be an alkali metal,such as potassium (K) or sodium (Na), or may be an alkaline earth metal,such as calcium (Ca) or barium (Ba), or may be ammonium (NH₄), or may beammonium derivatives, “X” may have a value of about 1 to about 2, and“Y” may have a value of about 0 to about 2. Furthermore, the F-ioncontained in the etchant may be hydrofluoric acid (HF), ammoniumfluoride (NH₄F), potassium fluoride (KF), sodium fluoride (NaF), orammonium hydrogen fluoride (NH₄HF).

[0037] The organic acid may be acetic acid (CH₃COOH), formic acid(HCOOH), oxalic acid ((COOH)₂), citric acid (C₆H₈O₇), or glycolic acid(HOCH₂COOH). Accordingly, the organic acid may determine a hydrogenionconcentration (pH) of the etchant to control the etch ratio of theetchant.

[0038] The Cu etch inhibitor may be an azole compound, such asmethylimidazole (C₄H₆N₂) and pyrazole (NHNH₂), or may be a triazolecompound, such as tolytriazole (CH₃N₃) and benzotriazole (C₆H₅N₃).Accordingly, the Cu etch inhibitor may prevent the etchant having theextracted copper ions (Cu²⁺) from etching out the copper layer, therebyrestraining an increase of a copper etching ratio.

[0039] The H₂O₂ stabilizer may be an acetate, such as ammonium acetate(CH₃COONH₄), potassium acetate (CH₃COOK), or sodium acetate (CH₃COONa).

[0040]FIG. 4 is a graph showing an exemplary relationship between etchtimes of a copper layer and concentrations of hydrogen peroxide (H₂O₂)according to the present invention. In FIG. 4, the copper layer used mayhave a thickness of about 2000 Å. As shown in FIG. 4, as the H₂O₂concentration increases, the etch time of the copper layer decreases.However, the etch time of each of titanium (Ti), tantalum (Ta), andaluminum (Al) does not vary by the H₂O₂ concentration since Ti, Ta, andAl are not effected by the hydrogen peroxide (H₂O₂). According to thepresent invention, the H₂O₂ concentration in the etchant may be within arange from about 4% to about 40%.

[0041]FIG. 5 is a graph showing another exemplary relationship betweenetch times of a copper layer and concentrations of potassium dihydrogenphosphate (KH₂PO₄) according to the present invention. In FIG. 5, thecopper layer may have a thickness of about 2000 Å. As shown in FIG. 5,as the KH₂PO₄ concentration increases, the etch time of the copper layerdecreases. However, the etch time of each of titanium (Ti), tantalum(Ta), and aluminum (Al) does not vary by the KH₂PO₄ concentration sinceTi, Ta, and Al are not effected by the potassium dihydrogen phosphate(KH₂PO₄). According to the present invention, the KH₂PO₄ concentrationin the etchant may be within a range from about 0.5% to about 10%.

[0042]FIG. 6 is a graph showing another exemplary relationship betweenetch times of a copper layer and concentrations of 4-methylimidazole(C₄H₆N₂) according to the present invention. In FIG. 6, the copper layermay have a thickness of about 2000 Å. As shown in FIG. 6, as the4-methylimidazole concentration increases, the etch time of the copperlayer also increases. According to the present invention, the4-methylimidazole concentration may be within a range from about 0.2% toabout 1.5%. For example, since the Cu etch inhibitor (e.g.,4-methylimidazole (C₄H₆N₂)) reacts with the Cu etching compound insteadof the copper, it prevents fast copper etching and restrains theincrease of a copper etching ratio.

[0043]FIG. 7 is a graph showing another exemplary relationship betweenetch times of metallic layers and concentrations of ammonium bifluoride(NH₄HF₂) according to the present invention. In FIG. 7, metallic layersmay be titanium (Ti), tantalum (Ta), and aluminum alloys, such as AlNd,and may each have a thickness of about 1000 Å. As shown in FIG. 7, asthe F-ion concentration increases, the etch time of the metallic layersdecreases. Although not shown, the etch time of the copper layer alsodecreases, as the F-ion concentration increases. According to thepresent invention, the F-ion concentration may be within a range fromabout 0.01% to about 5%.

[0044] According to the present invention, when etching Cu-aluminumalloy (Cu—AlNd) double layer structures using the etchant compoundsdescribed above, the etched double layer structures may be obtained, asshown in FIGS. 8-10. For example, the Cu layer may have a thickness ofabout 2000 Å, and the AlNd layer may have a thickness of about 200 Å.

[0045]FIG. 8 is a photomicrograph showing an exemplary interfacialcondition between a partially-etched copper/aluminum alloy (Cu/Al-alloy)double layer and an overlaying insulator according to the presentinvention. In FIG. 8, a double-layered metal layer structure may includea Cu layer 92 and an Al-alloy layer 90, such as AlNd, and may bepartially etched using the etchant according to the present inventiondescribed above. In addition, an insulator 94 may be formed on thedouble-layered metal layer structure. According to the presentinvention, and as shown in FIG. 8, delamination does not occur betweenthe overlying insulator 94 and the underlying double-layered metal layerstructure. Thus, deposition defects may be prevented.

[0046]FIG. 9 is a photomicrograph showing an exemplary slope of apartially-etched copper/aluminum alloy (Cu/Al-alloy) double layeraccording to the present invention. In FIG. 9, an AlNd layer 90 and a Culayer 92 may be sequentially formed as an AlNd-Cu double layerstructure. Then, the AlNd-Cu double layer structure may besimultaneously etched using the etchant according to the presentinvention, as described above. As a result, the AlNd-Cu double layerstructure may have a relatively gentle slope Θ without having anoverhang structure in which the underlying AlNd layer 90 is over-etchedbelow the overlying Cu layer 92.

[0047]FIG. 10 is a photomicrograph of an exemplary partially-etchedcopper/aluminum alloy (Cu/Al-alloy) double layers according to thepresent invention. The double-layered metal pattern structure ofCu/Al-alloy may have a relatively gentle slope along its patternedsides. Furthermore, when the double-layered metal layer structure ofCu/Al-alloy is patterned using the etchant according to the presentinvention, the patterned side of the double-layered metal layerstructure of Cu/Al-alloy may have a relatively straight line shape H. Asa result, the etchant according to the present invention has anincreased etching ability, and the patterned double layer structures mayhave improved patterned shapes.

[0048] Moreover, the etchant according to the present invention may notonly etch the Cu—Al-alloy double layer structures, but may also etch theCu—Al, Cu—Ti, and Cu—Ta double layer structures. In addition, theetchant according to the present invention may have an improved abilityto etch the Cu—Ti alloy and Cu—Ta alloy double layer structures.

[0049]FIGS. 11A to 11EC are cross sectional views of an exemplary methodof fabricating of an array substrate according to the present invention.In FIG. 1 1A, aluminum (Al) or an Al-alloy may be formed on a substrate100. Then, copper (Cu) may be subsequently formed over the substrate100, thereby forming a first metal layer 102 of aluminum or an aluminumalloy and a second metal layer 104 of copper. Next, the double metallayer structure of Al/Cu or Al-alloy/Cu may be patterned using theetchant according to the present invention, as descibed above.Accordingly, the etchant may include hydrogen peroxide (H₂O₂), aphosphoric acid (or phosphate), F-ions, an organic acid having acarboxyl group (—COOH), a copper (Cu) inhibitor, a H₂O₂ stabilizer, andan additive to improve the etching properties. An exemplary amount ofthe hydrogen peroxide (H₂O₂) may be within a range from about 4% toabout 40%, an exemplary amount of the phosphate may be within a rangefrom about 0.5% to about 10%, and an exemplary amount of the organicacid may be within a range from about 0.5% to about 10%. Furthermore, anexemplary amount of the Cu etch inhibitor may be within a range fromabout 0.2% to about 1.5%, an exemplary amount of the H₂O₂ stabilizer mayhave about a 1% concentration, and an exemplary amount of the additivemay have about a 1% concentration.

[0050] In FIG. 11B, after etching the Al/Cu or Al-alloy/Cu double layerstructure, a double-layered gate line 108 and a double-layered gateelectrode 106 may be formed on the substrate 100. For example, the gateline 108 may be disposed horizontally on the substrate 100, and the gateelectrode 106 may be elongated from the gate line 108. Furthermore, agate insulating layer 110 may be formed on the substrate 100 to coverthe double-layered gate electrode 106 and the gate line 108, wherein thegate insulating layer 110 may be formed of silicon nitride (SiN_(x)) orsilicon oxide (SiO₂). Next, pure amorphous silicon (a-Si:H) and dopedamorphous silicon (n+a-Si:H) may be subsequently deposited on the gateinsulating layer 110, and patterned to form an active layer 112 on thegate insulating layer 110 and an ohmic contact layer 114 on the activelayer 112. For example, the active layer 112 and the ohmic contact layer114 may be disposed over the double-layered gate electrode 116.

[0051] In FIG. 11C, a third metal layer 116 and a fourth metal layer 118 may be formed on the gate insulating layer 110 to cover the activelayer 112 and the ohmic contact layer 114. The third metal layer 116 maybe formed of one of titanium (Ti), Ti-alloy, tantalum (Ta), andTa-alloy, and the fourth metal layer 118 may be formed of copper (Cu).Alternatively, the third metal layer 116 may be aluminum (Al) or anAl-alloy instead of Ta or Ti. However, when Al or an Al-alloy is used toform the third metal layer 116, a buffer layer may be required betweenthe ohmic contact layer 114 and the third metal layer 116 to be formedof Al or an Al-alloy since the aluminum atoms may penetrate into theunderlying ohmic contact layer 114 and ohmic contact layer 112.

[0052] In FIG. 11D, the third and fourth metal layers 116 and 118 may besimultaneously patterned using the etchant according to the presentinvention, as described above, thereby forming a double-layered sourceelectrode 116, a double-layered drain electrode 118, and adouble-layered data line 120. The source and drain electrodes 116 and118 may contact the ohmic contact layer 114, and the data line 120 maybe disposed longitudinally perpendicular to the double-layered gate line108. Then, a passivation layer 124 may be formed over an entire surfaceof the substrate 110 to cover the double-layered source and drainelectrodes 116 and 118 and the double-layered data line 120. Thepassivation layer 124 may be an inorganic material, such as siliconnitride (SiNX) or silicon oxide (SiO2), or may be an organic material,such as benzocyclobutene (BCB) or an acrylic resin. Next, thepassivation layer 124 may be patterned to form a drain contact hole 126that exposes a portion of the double-layered drain electrode 118.

[0053] In FIG. 11E, a transparent conductive material may be depositedon the passivation layer 124, and patterned to form a pixel electrode128. The transparent conductive material may be indium tin oxide (ITO)or indium zinc oxide (IZO), and the pixel electrode 128 may contact thedouble-layered drain electrode 118 through the drain contact hole 126.Accordingly, the array substrate having the double-layered metal patternstructure formed of Cu and other metals may be completed.

[0054] According to the present invention, the double layers includingCu/Al, Cu/Al-alloy, Cu/Ti, Cu/Ti-alloy, Cu/Ta, or Cu/Ta-alloy may beused for gate and data lines and for electrodes of the TFT since theetchant according to the present invention may simultaneously etch thedouble layer structures. Furthermore, the etchant may provide superiorpattern profiles, thereby forming gentle slopes and uniform etchingcharacteristics. Since the etchant according to the present inventionmay simultaneously pattern the double-layered copper structures,fabrication processes may be reduced and fabrication yield may beincreased. Accordingly, the array substrate including the double-layeredcopper lines and electrodes may be used for large-sized LCD panels sincecopper has relatively low electrical resistance.

[0055] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the etchant for etching adouble-layered copper structure and method of forming an array substratehaving double-layered copper structures of the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An etchant for forming double-layered signallines and electrodes of a liquid crystal display device, comprising:hydrogen peroxide (H₂O₂); a phosphate; F-ions; an organic acid having acarboxyl group (—COOH); a copper (Cu) inhibitor; and a hydrogen peroxide(H₂O₂) stabilizer, wherein each of the double-layered signal lines andelectrodes of the liquid crystal display device includes a first layerof one of aluminum (Al), aluminum alloy (Al-alloy), titanium (Ti),titanium alloy (Ti-alloy), tantalum (Ta), and a tantalum alloy(Ta-alloy) and a second layer of copper (Cu).
 2. The etchant accordingto claim 1, wherein a concentration of hydrogen peroxide (H₂O₂) iswithin a range from about 4% to about 40%, a concentration of thephosphoric acid is within a range from about 0.5% to about 10%, aconcentration of the F-ions is within a range from about 0.01% to about5%, a concentration of the organic acid is within a range from about0.5% to about 10%, a concentration of the Cu etch inhibitor is within arange from about 0.2% to about 1.5%, and a concentration of the H₂O₂stabilizer is about 1%.
 3. The etchant according to claim 1, wherein thephosphate has a chemical formula of A_(X)H_(Y)PO₄, wherein “A” is one ofan alkali metal and an alkaline earth metal, “X” has a value within arange of about 1 to about 2, and “Y” has a value within a range of about0 to about
 2. 4. The etchant according to claim 3, wherein the alkalimetal is one of potassium (K) and sodium (Na), and the alkaline earthmetal is one of calcium (Ca) and barium (Ba).
 5. The etchant accordingto claim 3, wherein the phosphate includes one of ammonium (NH₄) andammonium derivatives.
 6. The etchant according to claim 1, wherein theorganic acid is one of acetic acid (CH₃COOH), formic acid (HCOOH),oxalic acid ((COOH)₂), citric acid (C₆H₈O₇), and glycolic acid(HOCH₂COOH),
 7. The etchant according to claim 1, wherein the Cu etchinhibitor is an azole compound selected from a group consisting ofmethylimidazole (C₄H₆N₂) and pyrazole (NHNH₂).
 8. The etchant accordingto claim 1, wherein the Cu etch inhibitor is a triazole compoundselected from a group consisting of tolytriazole (CH₃N₃) andbenzotriazole (C₆H₅N₃).
 9. The etchant according to claim 1, furthercomprising an additive having about a 1% concentration, wherein theadditives are salicylic acid derivatives.
 10. The etchant according toclaim 1, wherein the H₂O₂ stabilizer is acetate selected from a groupconsisting of ammonium acetate (CH₃COONH₄), potassium acetate (CH₃COOK),and sodium acetate (CH₃COONa).
 11. The etchant according to claim 1,wherein the F-ion is a fluoride selected from a group consisting ofhydrofluoric acid (HF), ammonium fluoride (NH₄F), potassium fluoride(KF), sodium fluoride (NaF), and ammonium hydrogen fluoride (NH₄HF). 12.A method of forming an array substrate of a liquid crystal displaydevice, comprising: forming a first metallic layer on a substrate;forming a first copper (Cu) layer on the first metallic layer;patterning the first metallic layer and the first Cu layersimultaneously using a first etchant to form a gate line and a gateelectrode, the first etchant includes hydrogen peroxide (H₂O₂), aphosphate, F-ions, an organic acid having a carboxyl group (—COOH), acopper (Cu) inhibitor, and a hydrogen peroxide (H₂O₂) stabilizer;forming a gate insulating layer over an entire surface of the substrateto cover the gate line and the gate electrode; forming an active layerand an ohmic contact layer on the gate insulating layer and over thegate electrode; forming a second metallic layer and a second copper (Cu)layer over the gate insulating layer to cover the active layer and theohmic contact layer; patterning the second metallic layer and the secondCu layer simultaneously using a second etchant to form a sourceelectrode, a drain electrode, and a data line, the second etchantincludes hydrogen peroxide (H₂O₂), a phosphate, F-ions, an organic acidhaving a carboxyl group (—COOH), a copper (Cu) inhibitor, and a hydrogenperoxide (H₂O₂) stabilizer; forming a passivation layer over the gateinsulating layer to cover the source and drain electrodes and the dataline, the passivation layer having a drain contact hole exposing aportion of the data line; and forming a pixel electrode on thepassivation layer, the pixel electrode contacting the drain electrodethrough the drain contact hole.
 13. The method according to claim 12,wherein the gate insulating layer is an inorganic material selected froma group consisting of silicon nitride and silicon oxide, and the pixelelectrode is formed of a transparent conductive material selected from agroup consisting of indium tin oxide and indium zinc oxide.
 14. Themethod according to claim 12, wherein the first metallic layer is one ofaluminum (Al) and an aluminum alloy (Al-alloy).
 15. The method accordingto claim 12, wherein the second metallic layer is one of titanium (Ti),tantalum (Ta), titanium alloy (Ti-alloy), and a tantalum alloy(Ta-alloy).
 16. The method according to claim 12, wherein aconcentration of the hydrogen peroxide (H₂O₂) is within a range fromabout 4% to about 40%, a concentration of the phosphoric acid is withina range from about 0.5% to about 10%, a concentration of the F-ions iswithin a range from about 0.01% to about 5%, a concentration of theorganic acid is within a range from about 0.5% to about 10%, aconcentration of the Cu etch inhibitor is within a range from about 0.2%to about 1.5%, and a concentration of the H₂O₂ stabilizer is about 1%.17. The method according to claim 12, wherein the phosphate has achemical formula of A_(X)H_(Y)PO₄, wherein “A” is one of an alkali metaland an alkaline earth metal, “X” has a value within a range of about 1to about 2, and “Y” has a value within a range of about 0 to about 2.18. The method according to claim 17, wherein the alkali metal is one ofpotassium (K) and sodium (Na), and the alkaline earth metal is one ofcalcium (Ca) and barium (Ba).
 19. The method according to claim 17,wherein the phosphate includes one of ammonium (NH₄) and ammoniumderivatives.
 20. The method according to claim 12, wherein the organicacid is one of acetic acid (CH₃COOH), formic acid (HCOOH), oxalic acid((COOH)₂), citric acid (C₆H₈O₇), and glycolic acid (HOCH₂COOH),
 21. Themethod according to claim 12, wherein the Cu etch inhibitor is an azolecompound selected from a group consisting of methylimidazole (C₄H₆N₂)and pyrazole (NHNH₂).
 22. The method according to claim 12, wherein theCu etch inhibitor is a triazole compound selected from a groupconsisting of tolytriazole (CH₃N₃) and benzotriazole (C₆H₅N₃).
 23. Themethod according to claim 12, further comprising an additive havingabout a 1% concentration, wherein the additives are salicylic acidderivatives.
 24. The method according to claim 12, wherein the H₂O₂stabilizer is acetate selected from a group consisting of ammoniumacetate (CH₃COONH₄), potassium acetate (CH₃COOK), and sodium acetate(CH₃COONa).
 25. The method according to claim 12, wherein the F-ion is afluoride selected from a group consisting of hydrofluoric acid (HF),ammonium fluoride (NH₄F), potassium fluoride (KF), sodium fluoride(NaF), and ammonium hydrogen fluoride (NH₄HF).